Valves are commonly used in devices that involve the transportation of a fluid. A typical type of valve, for example used in laboratory systems of moderate sizes such as a liquid chromatography system (LCS), is the rotary valve.
Generally, a rotary valve has a stationary body, herein called a stator, which co-operates with a rotating body, herein called a rotor.
The stator is provided with a number of inlet and outlet ports. The ports are via bores in fluid communication with a corresponding set of orifices on an inner stator face. The inner stator face is an inner surface of the stator that is in fluid tight contact with an inner rotor face of the rotor. The rotor is typically formed as a disc and the inner rotor face is pressed against the inner stator face in rotating co-operation. The inner rotor face is provided with one or more grooves which interconnect different orifices depending on the rotary position of the rotator with respect to the stator.
Rotary valves can be designed to withstand high pressures (such as pressures above 30 MPa). They can be made from a range of materials, such as stainless steel, high performance polymeric materials and ceramics.
The number of inlets/outlets as well as the design of grooves in the rotator or the stator reflects the intended use of a specific valve.
A common type of multi-purpose valve has one inlet port (typically placed in the rotary axis of the valve) and a number of outlets ports that are placed equidistantly around the inlet port. The rotor has a single, radially extending groove that has one end in the rotary centre, thereby always connecting to the inlet, while the other end connects to any one of the outlets depending on the angular position of the rotor with respect to the stator. Such a valve is useful to direct a flow from the inlet to any of the outlets—one at a time.
Another type of valve is used to select one of a set of components, each component having an inlet and an outlet. An example of this is the 6-port ST valve available from Valco Instruments Co. Inc., which is illustrated in FIG. 1.
Four components 121-124, herein illustrated as capillary loops, may be connected to the stator of the valve. The valve stator also has an inlet port 132 and an outlet port 131. The valve rotor has two grooves 125, 126. The outer groove 125, that is in fluid communication with the inlet port 132, has an inwardly radially extending portion that connects to one end 127 of the selected component 124. At the same time, the inner groove 126, that is in fluid communication with the outlet port 131, has an outwardly radially extending portion that connects to the other end 128 of the selected component 124.
Thus, the user may pass a flow through the selected component while the other components are isolated from the valve inlet/outlet. Provided that the flow direction through the valve is always the same, the flow direction through each component is determined by how it is connected to the valve.
However, sometimes the user wishes to alternate the flow direction through the component. For example, in the case that the component is a chromatography column it is sometimes desirable to load the column in one direction and then eluate the trapped content using a reversed flow direction. With a prior art valve similar to the one described above, it is then necessary to redirect the flow using additional means, such as a flow redirecting valve.